1 /* Simple expression parser */ 2 %{ 3 #define YYDEBUG 1 4 #include <assert.h> 5 #include <math.h> 6 #include <stdlib.h> 7 #include "util/debug.h" 8 #define IN_EXPR_Y 1 9 #include "expr.h" 10 %} 11 12 %define api.pure full 13 14 %parse-param { double *final_val } 15 %parse-param { struct expr_parse_ctx *ctx } 16 %parse-param { bool compute_ids } 17 %parse-param {void *scanner} 18 %lex-param {void* scanner} 19 20 %union { 21 double num; 22 char *str; 23 struct ids { 24 /* 25 * When creating ids, holds the working set of event ids. NULL 26 * implies the set is empty. 27 */ 28 struct hashmap *ids; 29 /* 30 * The metric value. When not creating ids this is the value 31 * read from a counter, a constant or some computed value. When 32 * creating ids the value is either a constant or BOTTOM. NAN is 33 * used as the special BOTTOM value, representing a "set of all 34 * values" case. 35 */ 36 double val; 37 } ids; 38 } 39 40 %token ID NUMBER MIN MAX IF ELSE LITERAL D_RATIO SOURCE_COUNT EXPR_ERROR 41 %left MIN MAX IF 42 %left '|' 43 %left '^' 44 %left '&' 45 %left '<' '>' 46 %left '-' '+' 47 %left '*' '/' '%' 48 %left NEG NOT 49 %type <num> NUMBER LITERAL 50 %type <str> ID 51 %destructor { free ($$); } <str> 52 %type <ids> expr if_expr 53 %destructor { ids__free($$.ids); } <ids> 54 55 %{ 56 static void expr_error(double *final_val __maybe_unused, 57 struct expr_parse_ctx *ctx __maybe_unused, 58 bool compute_ids __maybe_unused, 59 void *scanner, 60 const char *s) 61 { 62 pr_debug("%s\n", s); 63 } 64 65 /* 66 * During compute ids, the special "bottom" value uses NAN to represent the set 67 * of all values. NAN is selected as it isn't a useful constant value. 68 */ 69 #define BOTTOM NAN 70 71 /* During computing ids, does val represent a constant (non-BOTTOM) value? */ 72 static bool is_const(double val) 73 { 74 return isfinite(val); 75 } 76 77 static struct ids union_expr(struct ids ids1, struct ids ids2) 78 { 79 struct ids result = { 80 .val = BOTTOM, 81 .ids = ids__union(ids1.ids, ids2.ids), 82 }; 83 return result; 84 } 85 86 static struct ids handle_id(struct expr_parse_ctx *ctx, char *id, 87 bool compute_ids, bool source_count) 88 { 89 struct ids result; 90 91 if (!compute_ids) { 92 /* 93 * Compute the event's value from ID. If the ID isn't known then 94 * it isn't used to compute the formula so set to NAN. 95 */ 96 struct expr_id_data *data; 97 98 result.val = NAN; 99 if (expr__resolve_id(ctx, id, &data) == 0) { 100 result.val = source_count 101 ? expr_id_data__source_count(data) 102 : expr_id_data__value(data); 103 } 104 result.ids = NULL; 105 free(id); 106 } else { 107 /* 108 * Set the value to BOTTOM to show that any value is possible 109 * when the event is computed. Create a set of just the ID. 110 */ 111 result.val = BOTTOM; 112 result.ids = ids__new(); 113 if (!result.ids || ids__insert(result.ids, id)) { 114 pr_err("Error creating IDs for '%s'", id); 115 free(id); 116 } 117 } 118 return result; 119 } 120 121 /* 122 * If we're not computing ids or $1 and $3 are constants, compute the new 123 * constant value using OP. Its invariant that there are no ids. If computing 124 * ids for non-constants union the set of IDs that must be computed. 125 */ 126 #define BINARY_LONG_OP(RESULT, OP, LHS, RHS) \ 127 if (!compute_ids || (is_const(LHS.val) && is_const(RHS.val))) { \ 128 assert(LHS.ids == NULL); \ 129 assert(RHS.ids == NULL); \ 130 RESULT.val = (long)LHS.val OP (long)RHS.val; \ 131 RESULT.ids = NULL; \ 132 } else { \ 133 RESULT = union_expr(LHS, RHS); \ 134 } 135 136 #define BINARY_OP(RESULT, OP, LHS, RHS) \ 137 if (!compute_ids || (is_const(LHS.val) && is_const(RHS.val))) { \ 138 assert(LHS.ids == NULL); \ 139 assert(RHS.ids == NULL); \ 140 RESULT.val = LHS.val OP RHS.val; \ 141 RESULT.ids = NULL; \ 142 } else { \ 143 RESULT = union_expr(LHS, RHS); \ 144 } 145 146 %} 147 %% 148 149 start: if_expr 150 { 151 if (compute_ids) 152 ctx->ids = ids__union($1.ids, ctx->ids); 153 154 if (final_val) 155 *final_val = $1.val; 156 } 157 ; 158 159 if_expr: expr IF expr ELSE expr 160 { 161 if (fpclassify($3.val) == FP_ZERO) { 162 /* 163 * The IF expression evaluated to 0 so treat as false, take the 164 * ELSE and discard everything else. 165 */ 166 $$.val = $5.val; 167 $$.ids = $5.ids; 168 ids__free($1.ids); 169 ids__free($3.ids); 170 } else if (!compute_ids || is_const($3.val)) { 171 /* 172 * If ids aren't computed then treat the expression as true. If 173 * ids are being computed and the IF expr is a non-zero 174 * constant, then also evaluate the true case. 175 */ 176 $$.val = $1.val; 177 $$.ids = $1.ids; 178 ids__free($3.ids); 179 ids__free($5.ids); 180 } else if ($1.val == $5.val) { 181 /* 182 * LHS == RHS, so both are an identical constant. No need to 183 * evaluate any events. 184 */ 185 $$.val = $1.val; 186 $$.ids = NULL; 187 ids__free($1.ids); 188 ids__free($3.ids); 189 ids__free($5.ids); 190 } else { 191 /* 192 * Value is either the LHS or RHS and we need the IF expression 193 * to compute it. 194 */ 195 $$ = union_expr($1, union_expr($3, $5)); 196 } 197 } 198 | expr 199 ; 200 201 expr: NUMBER 202 { 203 $$.val = $1; 204 $$.ids = NULL; 205 } 206 | ID { $$ = handle_id(ctx, $1, compute_ids, /*source_count=*/false); } 207 | SOURCE_COUNT '(' ID ')' { $$ = handle_id(ctx, $3, compute_ids, /*source_count=*/true); } 208 | expr '|' expr { BINARY_LONG_OP($$, |, $1, $3); } 209 | expr '&' expr { BINARY_LONG_OP($$, &, $1, $3); } 210 | expr '^' expr { BINARY_LONG_OP($$, ^, $1, $3); } 211 | expr '<' expr { BINARY_OP($$, <, $1, $3); } 212 | expr '>' expr { BINARY_OP($$, >, $1, $3); } 213 | expr '+' expr { BINARY_OP($$, +, $1, $3); } 214 | expr '-' expr { BINARY_OP($$, -, $1, $3); } 215 | expr '*' expr { BINARY_OP($$, *, $1, $3); } 216 | expr '/' expr 217 { 218 if (fpclassify($3.val) == FP_ZERO) { 219 pr_debug("division by zero\n"); 220 YYABORT; 221 } else if (!compute_ids || (is_const($1.val) && is_const($3.val))) { 222 assert($1.ids == NULL); 223 assert($3.ids == NULL); 224 $$.val = $1.val / $3.val; 225 $$.ids = NULL; 226 } else { 227 /* LHS and/or RHS need computing from event IDs so union. */ 228 $$ = union_expr($1, $3); 229 } 230 } 231 | expr '%' expr 232 { 233 if (fpclassify($3.val) == FP_ZERO) { 234 pr_debug("division by zero\n"); 235 YYABORT; 236 } else if (!compute_ids || (is_const($1.val) && is_const($3.val))) { 237 assert($1.ids == NULL); 238 assert($3.ids == NULL); 239 $$.val = (long)$1.val % (long)$3.val; 240 $$.ids = NULL; 241 } else { 242 /* LHS and/or RHS need computing from event IDs so union. */ 243 $$ = union_expr($1, $3); 244 } 245 } 246 | D_RATIO '(' expr ',' expr ')' 247 { 248 if (fpclassify($5.val) == FP_ZERO) { 249 /* 250 * Division by constant zero always yields zero and no events 251 * are necessary. 252 */ 253 assert($5.ids == NULL); 254 $$.val = 0.0; 255 $$.ids = NULL; 256 ids__free($3.ids); 257 } else if (!compute_ids || (is_const($3.val) && is_const($5.val))) { 258 assert($3.ids == NULL); 259 assert($5.ids == NULL); 260 $$.val = $3.val / $5.val; 261 $$.ids = NULL; 262 } else { 263 /* LHS and/or RHS need computing from event IDs so union. */ 264 $$ = union_expr($3, $5); 265 } 266 } 267 | '-' expr %prec NEG 268 { 269 $$.val = -$2.val; 270 $$.ids = $2.ids; 271 } 272 | '(' if_expr ')' 273 { 274 $$ = $2; 275 } 276 | MIN '(' expr ',' expr ')' 277 { 278 if (!compute_ids) { 279 $$.val = $3.val < $5.val ? $3.val : $5.val; 280 $$.ids = NULL; 281 } else { 282 $$ = union_expr($3, $5); 283 } 284 } 285 | MAX '(' expr ',' expr ')' 286 { 287 if (!compute_ids) { 288 $$.val = $3.val > $5.val ? $3.val : $5.val; 289 $$.ids = NULL; 290 } else { 291 $$ = union_expr($3, $5); 292 } 293 } 294 | LITERAL 295 { 296 $$.val = $1; 297 $$.ids = NULL; 298 } 299 ; 300 301 %% 302